​PSEUDAELURUS VS. ARCHAEOINDRIS

Left image by Jay Matternes. Right by Wiki user Smokeybjb.

Pseudaelurus were relatively slender ancient felids, ranging in size from a typical domestic house cat to a cougar. They were spread across the globe from North America to Europe, Africa, the Middle East, and Asia. Although this genus would later give rise to the sabre tooth cats, only one species shows some indication of having large canines (Pseudaelurus quadridentatus). Their slender proportions and shorter limbs probably allowed them to be swift hunters that were also able to climb trees.

Now let us look at Archaeoindrus: a gorilla-sized lemur with a robust skeleton and long arms. The only species found thus far, Archaeoindrus fontoynontii, weighed around 160 kg and was likely arboreal (tree-dwelling), feasting on leaves and the occasional piece of fruit and seeds plucked from nearby tree branches.​I think a small species of Pseudaelurus wouldn't bother A. fontoynontii. But if this hypothetical battle involves a larger, cougar-sized P. quadridentatus (and this may be the case given its higher seeding), then our giant lemur may be in for some trouble. I'm giving this fight to Pseudaelurus, assuming it can clamp its jaws down on Archaeoindrus's neck before batted away by those long arms.

DIMETRODON VS. AEGYPTOPITHECUS

Left image by Dimitri Bogdanov. Right image by Nobu Tamura.

The next battle features my childhood favourite 'not-a-dinosaur': Dimetrodon! Dimetrodon was a sail-backed, Early Permian synapsid, sometimes called a 'mammal-like reptile' but more correctly known as a 'non-mammalian synapsid'. Yes, we humans are synapsids, although our mammalian lineage did not directly evolve from Dimetrodon. Different species ranged in size from 1.7 to 4.6 m long, and weighed from 28 to 250 kg. It was a terrestrial predator that sometimes ventured into shallow water to feed on reptiles, fish, and large amphibians.

Aegyptopithecus (known from one species, A. zeuxis), was a small (50-90 cm) ancient primate from the Oligocene of Egypt. The shape and position of its humerus (upper arm bone) suggests that rather than swinging through trees, Aegyptopithecus used all four limbs to climb through branches and along tree trunks.

Sorry Aegyptopithecus, you don't stand a chance against Dimetrodon! The only way it could survive a direct confrontationwould be for it to use its cunning, agility, and small size to run circles around Dimetrodon and flee, thereby forfeiting the battle and automatically losing.

HOMO FLORIENSIS VS. PALAEOLOXODON

Left photograph by Karen Neoh. Right image by Heinrich Harder.

Homo floriensis was a short statured, 'hobbit' sized species of early human. They lived on the island of Flores in Indonesia between 190,000 and 50,000 years ago. They stood about 1 metre tall, were capable of making simple stone tools, and used fire to cook. These stone tools have been found alongside remains of the now extinct dwarf elephant Stegodon. They also had a small brain with a relatively large cognitive centre, similar in size to modern humans.

Palaeoloxodonwas a genus of ancient elephants that lived throughout Europe and Asia during the Pleistocene and Holocene. They had long, straight tusks that could grow up to 9 metres in length (depending on the species). One species of Asian Palaeoloxodon, P. namadicus, was around 4 to 5 metres tall at the shoulder, and was possibly the largest land mammal to have ever lived. It is thought that most of the Palaeoloxodon species went extinct due to the introduction of predatory species, including Homo heidelbergensis and other early humans.

Palaeoloxodon seems to have been hunted to extinction by various species of Homo across the globe. And H. floriensis probably knew how to hunt the dwarf elephants of Flores. But if this battle is between H. floriensis and a local species of Palaeoloxodon -- the gigantic P. namadicus -- my bet is on Palaeoloxodon to trample its enemy and win.

UPDATE: I was informed that the species of Palaeoloxodon taking part in the battle is the dwarf Palaeoloxodon falconeri! So my pick is actually for H. floriensis to win this one.

AMEBELODON VS. DEINOGALERIX

Left image by Jay Matternes. Right image by Stanton F. Fink.

And finally we come to the last 'Antecessor' division pair. Amebelodonwas an ancient proboscidean, an ancestor of modern elephants, that lived in North America during the Miocene. It had a pair of 1 metre long, flat, paired lower tusks that formed a 'shovel'-like scoop, and a pair of more normal looking upper tusks. The lower tusks were likely used to strip bark off trees and dig through vegetation. Various species were up to 3 metres long and 2.5-3 metres tall at the shoulder.

Deinogalerixwas a Miocene gymnure, a rat-like 'giant' hedgehog, which lived on islands off the coast of Italy. It was an ancestor of modern day moonrats and hedgehogs, and like modern moonrats, did not have quills. Measuring around 60 cm in length, and with a mouth full of sharp teeth, it likely fed on insects, small reptiles, and other small mammals.

I suppose that Deinogalerix could annoy Amebelodon enough that it quits the field of battle, but I think it's more likely that Amebelodon will accidentally step on and squish our hairy-protohedgehog contender.

And that's a wrap for my March Mammal Madness 'Antecessors' division picks!

Join in the fun by printing and filling out your own bracket (found here). Then watch the #2018MMM hashtag from the 12th of March and keep up to date with the battles and fascinating mammal facts!

For the uninitiated, March Mammal Madness (or MMM) is a fun fake hypothetical 'battle' between different species of animals, alive or extinct, using a sports-style bracket to guess or predict who you think will win. Then a team of biologists go onto Twitter and (having done their research beforehand and ranked/seed each animal from 1 to 16) 'live' tweet the battles and the final results using the hashtag #2018MMM.

Each hypothetical battle involves guessing what two animals would do if they met face-to-face: would one run away, or one hiss and try to make itself look scary, or yawn and not really care? Whoever quits the field of battle loses, whether they fought the opponent or not. Just look at the pairs of animals in the bracket for Round 1, pick who you think would win out of each pair, and then compare those pairs of winners in Round 2, and pick who would win, and so on until you decide who will win overall (Katie Hinde, who created MMM, has a detailed outline of exactly of the competition works here). In early rounds, the place of battle is in the higher seeded animal's habitat, giving them the home-ground advantage. But be cautious: a higher seeded animal won't always beat a lower seeded animal, because who knows what interesting behaviour or outside event will cause an upset!

The point of MMM is to discuss cool and interesting aspects of mammal biology and behaviour, all the while cheering for your favourite animal to win!

I'm filling out my bracket now, and I'm excited that there is an extinct mammal division this year, called the 'Antecessors'. Here's a brief run-down of the first four pairs in this division and who I'm picking to win Round 1. Check out my second post to see my picks for the rest of the Antecessor division.

Doedicurus vs. Jugulator

Right image by Pavel Riha. Left image (of a mammal similar to Jugulator) from Wikimedia Commons.

Doedicurus was a Pleistocene-Holocene glyptodont, a large armadillo-like mammal with an armoured body and a spiky tail club. They were around 4 metres long and could weigh up to 2,370 kg!

​Jugulator (not to be confused with the Judas Priest album of the same name) was a predatorial, possibly gliding, early mammal species that lived during the Cretaceous. Although the thought of a predator gliding through the air to pounce on its prey might sound terrifying, it probably only weighed around 750 grams (which is actually huge for an early mammal).​I think Doedicurus's size and armour will (obviously) help it win the day. Although, MMM is known to have upsets where unlikely contestants win...

Cynognathus vs. Thalassocnus

Left image by Nobu Tamura. Right image by Wiki user FunkMonk.

Cynognathus was a predatory therapsid (the ancient mammal lineage we're a part of) from the Middle Triassic. It was around 1.2 m long with a large head full of sharp teeth including two large canines.

​Thalassocnus, on the other hand, was a semi-aquatic, if not fully aquatic, giant marine sloth from the Miocene-Pliocene. It was approximately 2 m long, and although it could walk on land, had dense bones adapted to life in the ocean eating seaweeds. ​Thalassocnus may be at a disadvantage battling the wolf-like Cynognathus in the deserts and swamps of Triassic Africa, but with its strong forearms and claws, I think it can defend itself and might just win.

Thylacoleo vs. Procoptodon

Left image by Mauricio Antón. Right image by Nobu Tamura.

The Aussies are here! First up: Thylacoleo, the Pleistocene 'marsupial lion'. It had blade-like cheek teeth, a sharp thumb claw, and although it could run on land it probably didn't move very fast. They were around 1.5 m long and weighed on average around 130 kg. The diet of Thylacoleo has been the subject of much debate in the palaeontological community: some proposed that their specialised cheek teeth were used to slice vegetation, but it is more likely they used them to break bones of the prey they hunted or scavenged.​Procoptodon was a giant short-faced kangaroo that also lived during the Pleistocene in Australia. They stood between 1-2 m tall (depending on the species) and the largest weighed around 200 kg. Although they may have hopped (as you might expect based on how modern kangaroos move), some new research suggests that they instead walked like other bipedal animals (including humans) do!

If we assume that Thylacoleo was a predator, its sharp teeth and claws could have made quick work of a Procoptodon. Given that they both lived during the Pleistocene and would have encountered each other in the wild, it is possible that Thylacoleo was a specialised hunter of Procoptodon and other large marsupials. Procoptodon could have made a speedy getaway, but only if it could hop instead of walking or running. Hmm... I think I'll choose Thylacoleo to win, but I won't be terribly surprised if this turns out to be an upset.

Andrewsarchus vs. Nuralagus rex

Left image by Dimitri Bogdanov. Right image by Meike Köhler.

Andrewsarchus was a large, ferocious looking carnivore (or possibly a scavenging omnivore) from the Eocene of Mongolia. With a skull over 80 cm long, and a predicted overall length of 5 metres, it may have been the largest mammalian land predator to have ever lived. Its skull was actually thinner toward the nose and weaker than it might look from restorations. If it did hunt prey, they were probably smaller than itself.​Nuralagus rex was also a giant! But only when compared to modern rabbits and pikas. Like Procoptodon, and unlike modern rabbits, the stiff-backed Nuralagus likely couldn't hop. Coupled with small eyes and ears, it probably couldn't detect or flee from predators very well. Perhaps it didn't need to, as it lived on the island of Menorca during the Miocene that was devoid of large predators.

​I feel like this is obvious, but I'm choosing Andrewsarchus to win not only because of its shear size and comparitive power, but also because the isolated island species Nuralagus rex didn't evolve any defence mechanisms against predators.

It turns out that ancient birds including Archaeopteryx may have been too fat to sit on their eggs without breaking them.

Most modern birds will sit on clutches of eggs to incubate them (this is called 'contact incubation'). And the bird lineage stretches back to the Late Jurassic and Cretaceous (during the Mesozoic). But when did birds start to contact incubate their eggs? We know that these Mesozoic bird eggs were, on average, a lot smaller than modern bird eggs. Does this mean they were too fragile for the adults to sit on?

An obvious place to start might be to look at the fossil record for bird nests and eggs compared to the size (and weight) of the parents. But the problem is that we often don't know which Mesozoic bird laid the fossil eggs that have been found. And there aren't enough fossils of birds sitting in nests.​

Artist's restoration of Archaeopteryx following Carney's 2011 feather coloration study, indicating that at least some of the feathers on the animal were black. Illustration by Nobu Tamura.

​In a new paper, Deeming and Mayr (2018) decided to approach this problem from a different direction. They took fossils of 21 Mesozoic bird species (including Archaeopteryx, Confuciusornis, and Jeholornis) and predicted the size and shape of the eggs they could have laid from measuring the width of the pelvic canal (birth canal). From this, they predicted how heavy the eggs would have been, and how much weight they could bear before breaking. Finally, they estimated weight of the adult birds.

They found that the pelvic canal width of the Mesozoic birds ranged between 10 to 26 mm (except for a particularly hefty species, Sapeornis chaoyangensis, with a pelvic canal width of 42 mm). These birds likely laid eggs that were 8.6 to 33.9 mm wide (which are a similar size to fossil eggs already discovered). The eggs probably weighed between 0.6 to 10.8 grams (except for our hefty friend who probably laid 41 gram eggs). The birds themselves were calculated to weigh between 120 to 750 grams.

The authors found that these Mesozoic birds could not have contact incubated their eggs without breaking them. Modern birds of a similar weight to these ancient birds typically lay much larger eggs. These Mesozoic birds laid eggs only 25% of the weight you would expect from a similarly sized modern bird!

Of course the paper uses a lot of estimates for body mass and egg mass, so there may be room for movement in the calculations. And the authors state that without knowing exactly what shape ancient eggs were or how thick the shell was, it is difficult to prove their hypotheses. But for the moment, it seems that these Mesozoic birds most likely did not sit on their eggs.

The predicted body mass versus shell load mass (how much weight the eggs could bear) for the Mesozoic birds studied. This data is compared to modern (extant) bird mass versus shell load. Note how modern bird eggs can tolerate a much heavier load (seen by the red column) compared to the parents body mass (green and yellow columns) than the Mesozoic bird eggs. Figure from Deeming and Mayr, 2018).

I gave a TEDx talk late last year where I chatted about taphonomy and decay in the fossil record, in Japanese Buddhist paintings, and on Mars. If that sounds interesting to you, check out the video below!

Photograph of the amber specimen with a hatchling enantiornithine preserved within (a), with combined x-ray and micro-CT scan (b), and illustration of body outline and position (c). Figure from Xing et al., 2017.

The hatchling is from a now-extinct group of avialans called enantiornithines. It is a 'bird' in the broadest sense, but just not from the same lineage that modern-day birds belong to (the neornithes).

The preservation of this specimen is fantastic. The right foot is clearly visible with the podotheca, claw sheathes, and feathers still intact. More difficult to see is the head and neck of this hatchling, but with the help of micro-CT and x-ray, Xing et al. (2017) show that they are present and also well preserved.

How did this hatchling end up in a lump of amber? Amber is preserved tree sap or resin, and while tiny animals such as insects are normally the victims of sticky-sap entrapment, small vertebrates such as frogs, lizards, and (as described by the same authors in a previous paper) a small dinosaur or bird tail have also been known to get caught in ancient resin. As for this hatchling, the authors propose that only part of the body was covered in resin (either during or soon after death), with the rest of the body remaining uncovered and exposed to the elements. Later, a second resin flow covered the remainder of the body.

The sauropod dinosaur backbone (vertebra) with what appears to be a footprint pressed right in to the centrum (outlined in red). Image from the Isle of Wight County Press.

It seems extremely improbable, but it isn't impossible. In taphonomy, we always consider the effect of trampling on decomposing bodies: if a body is laying near a lake or other water source, then it is likely that many other animals will be passing through that area and accidentally walk over the body. This can crush and scatter bone, but I've never heard of a foot landing precisely on the body (centrum) of a vertebrae and leaving a footprint behind.

In this case, it seems a small theropod (meat-eating) dinosaur has walked over the top of a decaying sauropod (long-necked) dinosaur carcass, at one point stepping precisely on a vertebra.

​​From what I can see in the photograph, it appears that there is still some mudstone covering the centrum. I thought perhaps the footprint was in the mud layer covering the bone, but the articles I've read suggest that the theropod foot crushed the bone. The rest of the vertebrae has been preserved quite well. This sauropod must have been decayed enough so that the vertebrae had disarticulated and lay centrum-side up, with the centrum and bone marrow softening and rotting while the rest of the bone remained fairly solid before it was trodden on. Again, improbable, but not outside the realm of possibility.

I also considered whether the footprint was pressed into a muddy bank first, and the bone later laid on top of it, 'sticking' the two together. However for this to be the case, the footprint on the bone would have to be a cast of the original print and would appear raised off the surface of the bone, rather than sunken in like a mold.

I look forward to seeing a thorough examination of this specimen, as if this impression is a theropod footprint, it shows direct evidence of this small theropod and large sauropod co-existing in the same part of the ancient Wealden landscape.

The remains were part of a taphonomic experiment at the Forensic Anthropology Research Facility (FARF) in Texas, USA, where they were studying what types of scavengers visit human carcasses. They were left uncovered with cameras photographing anything that came to scavenge them. Imagine being the person reviewing those images, expecting to see coyotes, or racoons, or turkey vultures, and instead uncovering the first recorded instance of human bone-munching deer.

I think what's more creepy is that the deer is chewing on a human rib, and then STARES AT THE CAMERA. "Yeah, that's right. Now you know, and I know you know..."Image from Meckel et al. (2017).

​This is not the first case of a classically herbivorous (plant-eating) animal eating bones from rotting carcasses--a behaviour called osteophagy--but it is the first time a deer has been captured nibbling on human remains.

Herbivorous animals practice osteophagy when they need more phosphate, calcium, and other nutrients in their diet. Porcupines, giraffes, cows, and even tortoises have been seen chewing on bones, most often already dry and easily accessible bones like ribs.

When recording traces of tooth-marks on bones in the modern, archaeological, or palaeontological record, it is important to remember that not all scavengers that interact with carcasses are trying to consume flesh. And that while carnivorous scavengers typically eat soft tissue and fresh bone leaving behind puncture holes and pits, bone-eating herbivores chew on the ends of older bones with teeth normally used to eat plants leaving behind long scores and forked splinters.

The end of the deer-chewed human rib. After the researchers saw the photographs of the deer visiting the human carcass, they raced out to find the bones it had left behind. Image from Meckel et al. (2017).

The day has finally arrived... I am now Dr Caitlin Syme! My PhD thesis went through the various stages of PDF upload, revision, re-upload, approval, FINAL upload, and then I received the letter I'd been waiting for...

I'm looking for more 'normal' paid work while I apply for post-docs and museum-related jobs, but for now I can breathe a little easier. Thanks for joining me on this PhD journey, and I hope you continue to find these posts useful for understanding both PhD and post-PhD life. And to keep enjoying fossil and taphonomy related news, of course!

Warm, dark-brown, sticky tar oozes out of the ground at Rancho La Brea in California, creating deep lakes of asphalt belching forth bubbles of methane. These asphalt lakes, or tar seeps, are particularly hazardous to animals passing by, trapping and swallowing up carcasses whole. And the tar seeps at La Brea have been trapping animals and luring predators to their deaths for 50, 000 years.

Rancho La Brea has produced around 3 million Pleistocene and Holocene fossils belonging to hundreds of vertebrate, invertebrae, and plant species, including dire wolves, sabertooth cats, mammoths, ground sloths, hawks, geese, owls, snakes, frogs, scorpions, spiders, ants, beetles, poison oak, juniper, red cedar, and thistle. The majority of fossils belong to mammalian predators that probably attempted to eat rotting carcasses stuck in tar, then found themselves similarly stuck in the asphalt ooze, then died and decayed thus becoming new lures for passing predators and scavengers. But no-one is quite sure how long decay might take before the carcass becomes a less appetising jumble of asphalt-soaked bones, and if those bones separate from each other and are pushed along by currents while floating at the surface, or disarticulate after sinking to the bottom of the tar seep.

A new paper by Brown et al. (2017) explores these questions by using actualistic taphonomic experiments. The authors took limbs from carcasses of a modern mammalian predator, the bobcat (Lynx rufus), and placed them in wire cages that were then lowered into tar seeps in Chivo Canyon, California. Over 10 weeks, they removed a limb from the tar seep every 2 weeks and noted how much soft tissue had decayed, as well as the types of microbes feeding on the flesh and living in the tar.

Figure from Brown et al. (2017) showing the stages of soft tissue decay in tar pits. The severed bobcat legs were lowered in to the tar in wire mesh cages. After 7 days some bone is already visible, and after 40 days most of the tissue has been eaten away.

​They found that decay occurred surprisingly quickly and surmised that a rich bacterial community exists in the tar seep, ready and waiting to consume flesh. Their microbial tests showed the bacteria did not hitch-hike into the tar seep on the bobcat carcasses. We know that hundreds of petroleum-eating bacteria species already exist in the tar seeps - they produce the methane bubbles - but it now seems that there are bacteria living in these tar seeps that specialise in eating organic material.

The authors conclude that modern bobcat limbs take around 2-3 months to fully decay in tar seeps. It appears that without the presence of the experimental wire cage, their bones would disarticulate (separate) after only a few weeks. The authors propose that the majority of decay and disarticulation therefore occurs at or just below the surface of tar seep, with single bones then being buoyed along by wind or water currents. The authors admitted that while these smaller limbs portions immediately sank into the tar, larger bodies may float at the surface while decaying with parts of the body exposed to the elements, and plan to conduct more actualistic experiments using whole carcasses in the future. I'd like to see more data on the temperatures of the tar seep, and how that might speed up or slow down decay depending on the types of bacteria present. Overall, this is a very thoughtful and interesting paper, so check it out (if you can get past the paywall).

About the author

Dr Caitlin Symeis a palaeontologist studying the taphonomy (preservation state) of fossil non-avian dinosaurs, crocodiles and fish from the Winton Formation, Queensland, Australia. Think forensic science or CSI for fossils, and you're on the right track!

Posts on this blog focus mainly on vertebrate palaeontology and taphonomy, as well early career researcher (ERC) productivity tips and insights.